1. Field of the Invention
The present invention relates to the connection between a heat exchanger and external pipes. More particularly, the present invention relates to the connection between a panel material forming a heat exchanger and a tank and a pipe disposed for supplying or discharging a heat exchanging medium to or from the tank.
2. Related Art
A known heat exchanger, such as a heater core for vehicles, generally comprises a box-shaped capsule, i.e., a panel material, composed of side panels, i.e., panel surfaces, that extend at both sides of a top wall in the longitudinal direction thereof, and a bottom panel, i.e., a seat panel, for closing the opening part of the capsule in the upper and lower end positions or left and right end positions. In such a conventional heat exchanger, a plurality of heat exchanging tubes communicate with both tanks by having both end parts of the tubes connected to the bottom panels of both tanks, with heat exchanging fins being disposed between the heat exchanging tubes. In addition to the above arrangement, a pipe is fixed to a part of the side panel of the capsule for supplying or discharging a heat exchanging medium to or from the tank.
In the heater core for vehicles, the pipe for supplying or discharging the heat exchanging medium should be long enough to connect a rubber hose connected to the engine side to the tank. To directly fix the requisite long pipe to the capsule of the tank, a method is disclosed in Japanese Unexamined Patent Publication No. 4-359796. This method suggests connecting the long pipe to the tank by means of clamp as illustrated in FIGS. 10 and 11.
That is, tank 1 is composed of a capsule 2 and bottom panel 25 disposed in the upper and lower end positions respectively. Here, capsule 2 is made of a thin metal sheet and formed integrally with tank 1 so as to be a box with one side open. Bottom panel 25 is also made of a thin metal sheet. Bent part 26 bent upwards at a right angle with respect to bottom panel 25 along the edge thereof is fixed to capsule 2 by means such as brazing to form tank 1.
In the specified position of one of side panels 22 at capsule 2 of tank 1, such as one of the longitudinal end parts of tank 1, pipe fitting hole 3 is formed by press machining. Peripheral edge part 4a is formed around pipe fitting hole 3, and is concentric with pipe fitting hole 3 concurrently with the press machining of pipe fitting hole 3. Also concurrently with the press machining of pipe fitting hole 3, two circular concave parts are formed by press machining. The two circular concave parts are first flat part 6 concavely formed so as to constitute the annular plane towards the inside of tank 1 through the surface of side panel 22 and cylindrical part 5, and second flat part 8 concavely formed towards the inside of the tank 1 through first flat part 6 and second cylindrical part 7 in the radially inward position of first flat part 6 so as to constitute the annular plane which makes the inner peripheral edge of pipe fitting hole 3. As described above, cylindrical part 5 of first flat part 6 and second cylindrical part 7 of second flat part 8 constitute circles concentric with pipe fitting hole 3.
Pipe 10 is made of the same metal material as that of tank 1 and has approximately the same outside diameter as the inside diameter of pipe fitting hole 3. End part 11 is formed at one end of pipe 10, with end part 11 being fit into pipe fitting hole 3 and closely fitting the inner surface of peripheral part 4a. Flange part 12 is formed in a position connected to end part 11. Flange part 12 has dimensions set so as to lock with the inner peripheral surface of cylindrical part 5 of first flat part 6, the outside diameter of which being formed in side panel 22 of capsule 2.
Pipe 10 is fixed to capsule 2 of tank 1 by means of clamp 30, which is made of a highly elastic metal plate, such as a spring steel sheet, by bending the metal plate so as to be approximately U-shaped in the thickness direction so that end part 11 can be fit into pipe fitting hole 3 formed in side panel 22 of capsule 2 by caulking annular sealing material 18 to the outer periphery of end part 11, with annular sealing material 18 being trapped between second flat part 8 formed on side panel 22 of capsule 2, second cylindrical part 7 thereof and flange part 12.
By fixing pipe 10 to side panel 22 of capsule 2 of tank 1 of a heat exchanger by means of clamp 30, pipes having different bending angles according to the difference in vehicle model can be connected. However, as pipe 10 is fixed to side panel 22 of capsule 2 by means of only the elasticity of U-shaped clamp 30, the problem exists that the fixing strength is not sufficiently high. Another problem with this known fixing method is that use of clamp 30 requires extra cost and time for assembly. Yet another problem is that processing for forming cylindrical peripheral end part 4a for holding pipe 10 requires imparting a sufficient roundness to end part 4a and press machining to achieve this roundness is difficult.